The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested . Meat is easier to digest hence carnivores like tigers have a shorter small intestine.
ABSORPTION OF FOOD
These are finger like projections present in the inner lining of the small intestines which increase the surface area for absorption. The villa are richly supplied with blood vessels which take the absorbed food to eat and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues.
ASSIMILATION
It is the process of utilization of food for building up or replacement purposes and for obtaining energy.
ENGESTION OF FOOD
The unabsorbed food is sent into the large intestine where more villi absorb water from this material. The rest of the material is removed from the body via the anus. The exit of this waste material is regulated by the anal sphincter.
GLANDS ASSOCIATE WITH DIGESTIVE SYSTEM
- Liver :- It secrets bile which contains bile pigments and bile salts. The bile secreted by the liver cells is normally stored in the gall bladder.
- Salivary glands:- These are three pairs of salivary glands which secret an enzyme called ptyalin or salivary amylase which digests starch.
- Pancreas:- It lies parallel to and beneath the stomach. It is a large gland which secrets digestive enzymes ,hormones ,insulin and glucagon.